The present invention relates to media for transferring images and, in particular, to an image transfer sheet and a corresponding method for using the sheet in conjunction with ink jet printers.
Human beings have long been fascinated with transferring images from one media to another. In the 1960""s, children and adults alike used Silly Putty(copyright) to transfer images onto a wide range of other surfaces. One common example of this technique was to use Silly Putty(copyright) to transfer colored comics from the Sunday newspaper to another surface. A person would roll the Silly Putty(copyright) on the comic to transfer the image from the paper to the surface of the Silly Putty(copyright). The Silly Putty(copyright) would then be rolled onto another surface to transfer the comic to a surface such as a countertop.
The Silly Putty(copyright) approach worked fine for temporarily transferring comics or other images onto a limited range of hard surfaces, but not onto less rigid surfaces such as fabric T-shirts, for example. To transfer an image onto a T-shirt, an individual had to purchase a pre-printed iron-on transfer sheet. To use this product, the purchaser would place the sheet image-side-down onto a T-shirt and then iron the sheet to transfer the image onto the fabric of the shirt.
Iron-on image transfer sheets had a number of limitations, however. First, since the sheets were pre-printed, individuals purchasing these products were limited to selecting from a narrow range of standard image designs. The individual could not be creative and design their own image.
Second, these products required the end-user to be somewhat skilled when transferring the image onto the desired substrate, such as a T-shirt. If the end-user did not hold the image transfer sheet perfectly still while ironing it, the image on the shirt was blurred. Thus, the end result was that an individual using these products had to be satisfied with an end-product that did not meet their aesthetic criteria, or else throw the image-bearing substrate away and start all over again. Thus, these products did not permit the substrate to be re-used.
Another limitation of these products was that they required ironing to transfer the image to the substrate. As an alternative to ironing, images could be transferred to T-shirts and other substrates with a silk-screen process. Typically, silk-screening requires the user to place a custom order with a custom printer. However, by placing a custom order, the individual lost his/her opportunity to directly create his/her own personalized products. Additionally, the expense and time delay in receiving the final end-product were significant disadvantages to placing a custom order.
The image transfer field took a new turn in the 1990""s, when ink jet printers became widely popular. T-shirt transfer sheets were developed onto which a user could print a custom image using software installed on a personal computer, then use an ink-jet printer connected to the computer to print out the custom image in reverse form onto the T-shirt transfer sheet. The image on the T-shirt transfer sheet would then be transferred onto a T-shirt by laying the sheet print-side down on the substrate and then ironing the back side of the sheet. The printed image would then appear on the T-shirt. With the introduction of these products people could, for the first time, compose a custom image on their personal computer, then put that image onto a T-shirt using little more than an ink jet printer and an iron.
As examples of commercially available ink jet products for image transfer, Canon now sells an ink jet compatible iron-on T-shirt transfer sheet under the product code TR-101. Similarly, Hanes sells an ink jet compatible iron-on T-shirt transfer sheet under the trade name Hanes T-ShirtMaker. Both the Canon and Hanes sheets require heating the sheet with an iron or other hot device before the image will transfer. As an alternative to printing an image onto the Hanes sheet with an ink jet printer, the user may draw an image directly onto the sheet with special crayons and then iron the crayoned image onto a T-shirt.
While these types of sheets represent a step forward, they have various limitations. Many of the sheets transfer at most only about 60%-80% of the printed ink onto the substrate. Consequently, the colors do not appear as brilliantly on the substrate as they should, and images are not nearly as crisp. Secondly, the image is permanently fixed onto the T-shirt as soon as it has been ironed on. If the user does not like the image, or if the image did not transfer properly, there is no way to remove the image from the substrate. The user must either throw the substrate away and begin anew, or use the product in its flawed state.
A third limitation of these sheets is that the entire image sheet transfers with ironing, even areas that are not printed and that do not contain the image. For example, a circular printed pattern is often ironed on as a large square, leaving an unsightly square edge around the circular printed pattern and unnecessarily stiffening the substrate. As an alternative, the instructions for Canon""s product code TR-101 suggest cutting out the printed image from the image transfer sheet as follows:
xe2x80x9cFor best results, cut away the unprinted portion of the transfer, coming as close to the printed area as possible. If an unprinted portion of the transfer is applied to the fabric it will cause the fabric to become stiffxe2x80x9d
One problem with this approach is that it requires considerable cutting skill on the part of the user. If the user snips a little bit too far, he may cut into and thereby damage the printed image. If the image is at all intricate, considerable time may be necessary to cut about the image, and it may be impossible to remove the unprinted central portion of the transfer. Also, if the cut is not perfect, the unprinted area about the edge of the image may have an uneven, unsightly appearance once transferred to the substrate.
Fourth, the transfer sheets are generally designed to transfer images only with simultaneous heat transfer and fixing. This imposes an additional limitation as the user is frequently limited to selecting those fabrics or other surfaces that can accept the simultaneous heat transfer and fixation without being damaged. There are many instances when a user wants to transfer a custom-printed image onto surfaces that cannot be heated. For example, custom designed images and/or phrases cannot be ironed onto an automobile, or onto other surfaces such as glass windows, three-ring binders and tiles, to name a few. Other surfaces that are desirable for image transfer include paper of various types, file folders, report covers, sheet protectors, plastic and vinyl binders, glass, mirrors, cardboard, stainless steel, aluminum, painted metal, wood, ceramics, FORMICA(trademark), furniture, overhead transparencies, toys, and a wide variety of other surfaces.
Another drawback with some of the prior art T-Shirt image transfer sheets is that even after the image has been transferred, the shirt must be washed in a vinegar bath in order to set the image. The requirement of making the image permanent by immersing the image-bearing substrate into a vinegar bath adds yet another step to a complicated and hazardous process.
It is an object of the present invention to advance the art of image transfer sheets generally, and to overcome at least some of the problems in the prior art. The invention encompasses several embodiments of an image transfer sheet, and a method for manufacturing such sheets.
According to one aspect of the present invention, a cold image transfer process using no supplemental heat in the course of image transfer has a first step of forming an image transfer sheet having the following successive layers: a) a release-coated liner sheet; b) a layer of substantially water-accepting adhesive; and c) an ink jet transmissive detackifying (xe2x80x9cdetackxe2x80x9d) layer. An image is applied to the image transfer sheet from an ink jet printer. The image sheet is applied to a substrate at ambient temperature with the adhesive bonding directly to the substrate. The release-coated liner is then removed.
According to another aspect of the present invention, a wet coating of water-activatable adhesive is applied to a flexible substrate. The substrate is placed in an oven or dryer in order to dry the adhesive. Dehumidified air may be pumped into the oven in order to speed the drying process and thereby increase the rate of production and/or reduce the temperature of the oven without increasing drying time. A water-permeable detack layer may then be coated on the outer exposed surface of the adhesive layer to form the final construction. A printing press may be used to print one or more thin layers of the water-activatable adhesive and/or water-permeable detack layer onto a flexible backing sheet.
In one contemplated embodiment of an image transfer sheet, a water-activatable adhesive is first printed or coated onto a flexible backing layer, with the water-accepting adhesive being removable from the backing layer. The image transfer sheet has a water-impermeable layer in between the adhesive and the backing layer. The sheet may also have an optional detack layer that is applied onto the layer of adhesive, the layer of adhesive being in-between the detack layer and the flexible backing layer.
Different embodiments may include various additional features. The sheet may include a water-impermeable layer with the water-activatable adhesive being coated on the outer surface of the water-impermeable layer. The flexible substrate may alternatively be a paper that is release-coated on the side of the sheet to which the water-activatable adhesive is applied. The sheet may include a pigmented, colored, tinted, or reflective water-permeable layer in between the detack coating and the adhesive layer, where dyes, tints, pigments and metallic flake pigments such as malachite green, titanium dioxide, calcium carbonate, powdered aluminum and aluminized polyethylene terephthalate (Mylar) are used to create the effect desired. At least a portion of the water-activatable adhesive layer and the water-permeable detack layer are together removable from the flexible substrate. The water-impermeable layer may be a varnish. The detack layer may comprise a mixture of polyvinyl alcohol (PVOH), polyacrylic acid (PAA) and starch. Alternatively, the detack layer is optional in some embodiments in which the adhesive is not tacky prior to printing. The adhesive layer may include acrylic copolymers, in which the copolymers are formed from a mixture of monomers comprising (a) one or more alkyl acrylates, (b) methyl acrylate, (c) vinyl acetate, and (d) methacrylic acid and/or acrylic acid.
According to another aspect of the present invention, an image transfer sheet is provided that permits the user to apply the image to a substrate, then decide whether to permanently bond the image to the substrate or to remove the image. For example, one versatile method includes printing an image onto one sheet from the supply with a water-based ink, thereby activating the adhesive only in the areas onto which water-based ink has been printed. The sheet is then applied to a first substrate to adhere the image to the substrate. After applying the sheet to the first substrate, the sheet is pulled off of the substrate to leave the portions of adhesive that bear the image attached to the substrate but leaving the portions of the adhesive that do not bear the image attached to the sheet.
At this point, if the user decides that the resulting image does not meet his/her aesthetic requirements or otherwise wants to remove the image, the user may do so. A second image is then printed onto another, second sheet of the image transfer sheet supply with a water-based ink, thereby activating the adhesive of the second image transfer sheet only in the areas of the second image transfer sheet onto which the water-based ink has been printed. That second image transfer sheet is then applied to the substrate to adhere the image to the substrate. After applying the sheet to the substrate, the sheet is pulled-off of the substrate to leave the portions of adhesive that bear the image attached to the substrate, but leaving the portions of the adhesive that do not bear the image attached to the sheet. If the user is now satisfied with the image, and where the substrate is capable of being heated by some heat source, the user may apply heat to the image-bearing substrate thereby making the image permanent and water-fast
In this way, a user sometimes makes an image permanent on the substrate by heating the image on the substrate. At other times the user does not heat the image, so that the image is only temporarily attached to the substrate and is ultimately removed therefrom. The stack of sheets that accept the images can therefore be used for a dual purpose: for the temporary transfer of images and/or for the permanent transfer of images, a feature not contemplated by the prior art.
The image-accepting sheet may be used for a variety of purposes. One such purpose is the production of multiple transferable images on a single sheet. The addition of a plurality of perforation lines on the sheeted stock results in the formation of a plurality of substantially rectangular or square portions. Thus, using software such as Avery Dennison""s Avery Kid""s or Printertainment Software to create a plurality of images on a computer screen, the user can print a multiplicity of images on the image-accepting sheet, with one or more images being printed on each rectangular or square portion of the image-accepting sheet to create an end-product sheet having a variety of separable, transferable images. The rectangular portions may then be separated with the aid of the perforation lines after the images have been printed onto the sheet. Other varieties of perforation shapes may be employed depending on the purpose for which the images will be used. For example, the sheet may be pre-die-cut or perforated to form a plurality of circles, squares, ovals, rectangles, etc. or a mix thereof. Smaller images may be transferred to baseball caps, shirt sleeves, pockets, doll clothes, household items such as pot holders, and the like. A second advantage of perforating the sheet is to allow the end-user to maximize the printable area of the sheet by permitting the end-user to print and then separate out the multiple images on a single sheet, thus avoiding any waste. As an alternative, the composite sheet could be die-cut, or scored, or otherwise provided with lines of weakness in order to replace some or all of the perforation lines. Further, the present invention is applicable to laminated sheet assemblies.
According to one embodiment of the present invention, a sheet for transferring an image that has been printed onto the sheet with a water-based ink has a flexible backing layer. A water-impermeable layer is coated or printed on to the backing layer. A water-accepting layer that includes a water-activatable adhesive is then printed onto the water-impermeable layer, the water-accepting layer being removable from the water-impermeable layer. A detack layer is then applied by printing or coating means onto the water-accepting layer.
The sheet may also have a variety of other features. For example, the sheet may include a water-permeable colored, tinted, pigmented or reflective (or some combination thereof layer in between the detack layer and the water-accepting layer. The sheet may have a water-permeable layer of cross-linker in between the detack layer and the water-accepting layer, wherein the water-accepting layer becomes water-resisting when water-based ink flows through the layer of cross-linker and into the water-accepting layer.
There are several contemplated approaches to making the image permanent or fixed. In one approach, the activated cross-linker can migrate into the pressure-sensitive adhesive to chemically fix the image. In this mode, the ink acts as the carrier facilitating the migration of the cross-linker into the adhesive. In another approach, a heat-activatable cross-linker may be added directly to the adhesive. Once activated, the cross-linker fixes the image. In yet another approach, a water-accepting layer that is initially porous to the ink, may on heat treatment, become non-porous and water-resisting thereby fixing the image. In this mode the water-accepting layer may comprise both adhesive and cross-linker. As a further alternative, an image transfer sheet may be provided having a water-permeable layer of adhesive coated or printed on the outer surface of a water-accepting image-holding layer. The adhesive acts to temporarily bond the image-holding layer to a substrate. To permanently bond the image holding layer to the substrate, the user heats the image-holding layer to make the image-holding layer water-resisting.
Other objects and features of the invention will become apparent from a review of the Detailed Description below, from the drawings, and from the claims.